The use of hydrogen gas as a supplemental fuel in addition to gasoline or gasohol offers some distinct advantages for present and future motor vehicle operation in the light of constantly increasing gasoline prices and projected supply diminishment. Hydrogen fuel can be readily adapted for use in conventional automotive I.C. engines with only minor adjustments necessary for its proper combustion along with gasoline or gasohol.
Since hydrogen gas burns cleanly with water vapor left as the major exhaust component, the total exhaust emission levels from such combined fuel for the engine will be correspondingly lower. These two advantage alone should be more than enough for hydrogen fuel to gain wide scale acceptance as a supplementary automotive fuel, but in addition hydrogen can be readily generated on-board the vehicle with retrofitted components, unlike any other fuel means now known.
The main effort towards the development of practical automotive hydrogen fueled vehicles has been by way of the storage of the gas on board the vehicle as the primary fuel source. The most prominent method used for the storage of the gas has been the utilization of various types of metal hydrides,-which act as hydrogen gas "sponges" to absorb and release the gas as required.
Such groups as Brookhaven Labs, Billings Corporation, and Mercedes Benz have adopted this on-board hydrogen storage method because of its workability, basic safety and useful gas volume storage capacity.
With the advent of iron-titanium hydride (Ti-Fe), developed at Brookhaven Laboratories, the on-board H.sub.2 storage approach for vehicular applications has become practical, since hydrogen can be absorbed and released from the storage volume at relatively low temperatures and pressures. While these various plus features for hydride storage make its use attractive for many vehicular applications there remains the major problem of hydrogen distribution to motorists which will be decades away from realization, if at all. The hydrogen distribution problem means that automotive hydrogen storage alone, cannot be considered as a short-term solution to ever increasing gasoline prices and the progressively decreasing supply.
The wide scale distribution of hydrogen as an automotive fuel will require long term capital investment by the industry, while on the other hand, on-board hydrogen generation equipment is centered on the first cost of operating components only, which do not now appear to be beyond the range of reasonable first cost amortization, based on the long-term gasoline cost savings involved.
Various types of hydrogen fueled vehicles have been proposed and described over the years with the prospects of substituting this minimum polluting fuel for high cost, polluting gasoline fuel, as presently used. There has been considerable reluctance towards the acceptance of hydrogen as a fuel because it is believed to be dangerous to handle and use,-(the Hindenburg syndrome) but if carefully generated and used immediately in minimum volumes, adequate safety is assured.
Considerable theoretical work has been done toward utilizing hydrogen as an alternate fuel for conventional I.C. engines with numerous hydrogen generation and storage methods proposed and developed. All of the economically practical and experimental methods for hydrogen generation have been described in about twenty prior U.S. and foreign patents for alternate vehicular propulsion. Several of these prior patents deal with heat recovery from the engine exhaust manifolds to drive various types of closed cycle engine loops, which in turn are used to provide a low voltage D.C. power source required for conventional electrolysis cells, as the hydrogen generation means.
Another on-board hydrogen generation means which has received moderate attention and prototype development effort is the gasoline reforming process in which a small flow volume of gasoline is broken down into its basic components in a thermal reactor, with hydrogen gas produced along with varying amounts of hydrocarbon by-products. Successful prototypes have been evolved using this process, but the present equipment is cumbersome and will require extensive size reduction and improvement before any possible commercialization stage is reached.
It should be realized that the gasoline reforming process for automotive applications starts out with a negative position, since it takes away a small portion of the total gasoline flow which we are attempting to conserve as an overall goal for an economical automotive supplemental fuel system.
The electrolysis process for automotive applications, previously mentioned, is not handicapped in this way, as it is clearly separate from the primary fuel supply, and although it is mainly dependent on I.C. engine operation, it is not dependant on the primary fuel means in any way. The major problem facing on-board hydrogen generation using the electrolysis process is that of the very large electrical wattage required and the relatively slow rate of hydrogen flow produced which is not now compatible with normal I.C. engine operation.
In a modifided steam-on-iron hydrogen generation process,--Bogan,--U.S. Pat. No. 3,653,364, has described the adaptation of this known H.sub.2 industrial process to an automotive application. Although this process art is novel in several respects it does not solve all the different problems involved in such a limited space and operating environment for this normally large scale industrial process. Firstly, the steam-on-iron process usually operates with the best effectiveness in the superheated steam ranges which are not economically possible for any automotive applications. Another major difficulty not considered in this art is that of the intermittant deoxidation/aeration of the iron volume-(contact mass), which is not feasible with stationary small iron balls, as described.
The oxidation of all the iron balls will gradually diminish as they all become fully rusted and the hydrogen liberation will correspondingly diminish and eventually come to a halt. If all of the small iron balls are uniformly agitated and periodically abraded to remove the rust/and/or accumulations in some way, then this method may be reasonably succesful for nearly continuous operation if a high temperature steam flow is provided within a suitable reaction unit.
High energy levels are required to produce the necessary steam reforming, and while a portion of the required heat energy can be recovered from the exhaust manifold(s), as described by Bogan, an additional high heating source will be required to maintain the thermal reaction for an automotive version of this industrial process. The use of electrical resistance heaters powered by the vehicle's only battery, as described by Bogan, is not considered practical in view of their constant high discharge rate from the single battery in the vehicle. It is not feasible to heat water into steam by electrical resistance heating as described by Bogan, and a more practical approach must be sought to produce the necessary steam flow.
In an earlier U.S. Pat. No. 1,966,345, by Harrell, iron filings are fully packed within a pipe section centrally located inside the exhaust manifold of an auto engine. A small steam flow is produced within the exhaust manifold from a raised water reservoir which gravity feeds a small water flow into the manifold and pipe section. While the steam flow over the iron filings will produce hydrogen liberation, again no provision for periodic purging is evident in this hydrogen generation arrangement, so that it falls short of a practical and continuous supplementary hydrogen fuel system for vehicles. This earlier art is more effective from the standpoint of heat transfer than the art of Bogan, since the iron filings within the pipe section is fully enclosed within an enlarged special exhaust manifold on a conventional I.C. automotive engine. The art of Bogan does not take the fullest advantage of the hot exhaust manifold(s) as does Harrell's art.
It can be appreciated that the very high exhaust manifold temperatures are attractive heat sources especially when no operating performance penalty is imposed on the vehicles engine or drive train. In spite of this attractive heat source for hydrogen liberation by steam reaction, an additional heat source will be required for a successful hydrogen fuel flow by this known method. The use of several electrical resistance ce heaters as the added heating means can be considered only if a second 12 volt automotive battery is included along with a constant and reliable recharging means for this second battery.
Such unusual electrical sources as thermoelectric and photovoltaic cells and air driven generators revolved by the moving vehicle can be useful electric recharging sources for this specific application. Since the multiple electrical heaters cause a large electrical drain on the secondary battery, it will be necessary to provide electrical recharging from all three electrical sources previously described.
The authority for the contention that an effective deoxidation aeration phase for the steam-on-iron process is necessary comes from "Bailey's Industrial Oil and Fat Products,"--Third Edition,--on Hydrogenation, Pg. 851, ie: "Failure to remove these accumulations-(carbon, sulfur, rust) results in virtually complete inactivation of the control mass (iron balls, iron fillings)." "It is customary to follow each steaming period with a short period of aeration (purging) during which time air is blown through the ore (constact mass) to burn off the carbon and sulfur accumulations."
While the purging of the contact iron mass in the industrial process can be readily accomplished, it becomes a difficult task to achieve for an automotive-sized unit(s) where both a lack of space along with purging provision and effectiveness become major difficulties.